Firing mechanism for automatic firearms



March 23, 1965 H. BRIEGER FIRING MECHANISM FOR AUTOMATIC FIREARMS FiledFeb. 8, 1962 a e r W W fw H I .m a H H United States Patent 3,174,399FIRING MECHANISM FOR AUTOMATIC FIREARMS Hans Brieger, Zurich,Switzerland, assignor to Machine Tool Works Oerlikon AdministrationCompany, Zurich- Oerlikon, Switzerland Filed Feb. 8, 1962, Ser. No.171,874 Claims priority, application Switzerland, Feb. 13, 1961, 1,697/61 4 Claims. (Cl. 89-132) The invention relates to a firing mechanismfor automatic firearms having a device for the displacement of a scarbetween a release position, in which a lock catch arranged on it isoutside the range of an engaging portion of the breech bolt, and anengaging position, in which the lock catch engages into the path onwhich said engaging portion runs during the forward movement and therecoil stroke of the breech bolt, and having detent means co-operatingwith said displacement device for locking said sear in the releaseposition.

With a known firing mechanism proposed for attaining a full area contactof the engaging surfaces the locking device, which is mounted on thesupport of the weapon, is controlled by a component taking part in therecoil movement of the weapon relative toits support and forming thecontrol device, in such a manner that the release of a lock catch ispossible during the period at the end of the return of the weapon intothe firing position and at the beginning of its recoil.

Such a construction assumes that the weapon is mounted moveably in sucha manner that it advances after each recoil into a well defined startingposition. When however the device controlling the recoil and forwardmove ments of the weapon is laid out for certain reasons in such amanner that the weapon during the firing of a series of shots does notreturn to the starting position occupied at the beginning of the firing,but is braked at any time already during its advance and thrown back bythe action of the following shot, the lengths of the advance paths ofthe individual shots may differ from one another, as well known. Whenusing the aforesaid known firing mechanism with such a weapon having afloating mounting, it may happen that the locking device cannot bebrought at all by the control device out of the release position duringthe individual intervals between shots.

The present invention has the primary object of obviating thisdisadvantage. With this and other objects in view, which will becomeapparent later from this specification and the accompanying drawing, Iprovide a firing mechanism for automatic fire arms comprising incombination: a stationary breech casing, a support, a breech bolt havingan initial position in operation reciprocating under the influence of areturn spring longitudinally over said breech casing, a scar having alock catch pivotally mounted relative to said support, a displacementdevice operatively connected with said sear and displacing the latterbetween a release position, wherein said lock catch is kept outside therange of the engaging portion of said reciprocating breech bolt, and aholding position, wherein said lock catch engages into the path of saidreciproeating breech bolt, during the recoil and advance thereof, anddetent means co-operating with said displacement device in the sense oflocking said sear in the release position, said breech bolt during thelast part of its recoil stroke and first part of its forward strokewhile its engaging portion is behind said sear, locking saiddisplacement device by means of said detent means against displacement,and against displacement of said sear into the holding position.

These and other features of my said invention will be clearly understoodfrom the following description of a 3,174,399 Patented Mar. 23, 1965"ice preferred embodiment thereof given by way of example with referenceto the accompanying drawing diagrammatically illustrating my new firingmechanism in longitudinal section in various functional positions,namely:

FIG. 1 illustrates the initial position.

FIG. 2 the release position, e.g. the firing position with the triggeractuated.

FIG. 3 the transitory position from the release position to the holdingposition.

Referring first to FIG. 1, a casing 2 containing the firing mechanism isattached on the parts 1 of the breech casing. In the lower portion ofthe casing 2 the buffer spring 4 with damping elements is arranged fortaking the impact when engaging the breech bolt 3. Alternativelyself-damping annular disc springs may be provided. One end of thisspring abuts the casing 2 and the other end abuts a sleeve 5 which islongitudinally slidable in the casing 2. The sleeve 5 has a cam 5aengaging into a slot 6 of the support 7 and abutting the latter. Thissupport 7 has a groove-shaped recess and is mounted in the casing 2, alocking slide 8 forming part of the displacement device and being guidedin the interior of easing 2. The forward portion of said locking slidehas two faces 8a and 8b. Two roof-like converging abutment cam faces and8b are arranged ahead of an aperture 9, intowhich engages one arm 10b ofa two-armed trigger 10 pivotally mounted on a pivot 11 fixed to thecasing 2. The second arm 10a thereof abuts a face 12 which can be raisedand lowered when actuating the trigger mechanism (not shown).

The casing 2 is connected with a spring sleeve 13, in the bore of whicha bushing 14 is moveably mounted. The latter is subject to the bias of aspring 15 abutting the end-wall of said sleeve, and bears on the wall 8eof the locking slide 8, applying a pressure on it in the directiontowards the wall 2a of the casing 2. The displacement device comprisesin addition to the locking slide 8, trigger 10, face 12 and triggermechanism also the sleeve 13, bushing 14 and spring 15.

Referring now to FIG. 2, a sear 16 is pivotally mounted on a pivot 17fixed to the side walls of the support 7. As will be seen in thisfigure, a lock catch 18 having an engaging face 18a is inserted into thesear 16 rotatably about a pivot 19. The pivot of this lock catch 18 andof the sear 16 are so arranged that a force applied substantiallyperpendicular to the engaging face 18a acts on the sear 16 in the senseof turning the same clockwise, while the same force acts on the lockcatch 18 in the sense of turning the latter anticlockwise about thepivot 19, forcing thereby the lock catch 18 against the face 16a of thesear 16 and thus assisting the action of a spring 20. Moreover the sear16 has a supporting face 16b, a projection 21 with the faces 21a and21b, as well as a bearing surface upon which the spring 28 from thesupport 7 passes.

Referring now to FIG. 3, a tumbler 22 is mounted on the support 7pivotally about a pivot 23, the face 22a of which tumbler 22 is convexlycurved towards the path of the breech bolt 3. On the tumbler 22 a detentmember 24 is mounted pivotally about the pivot 25, and moreover in abore of said tumbler a spring 26 is housed, which abuts the springsleeve 13 and bears on the detent member 24 tending to turn the same tothe positions illustrated in all three figures. The mounting of thedetent member 24 on the tumbler 22 is chosen in such a manner that saiddetent member 24 abuts said tumbler after a short movement. Moreover thespring 26 applies a bias to the tumbler 22 turning the sameanticlockwise about the pivot 23. It tends to turn the same into a restposition shown in FIGS. 1 and 2, in which its face 22b abuts the wall ofthe spring sleeve 13. The

3 detent member 24 is provided with a projection having faces 24b and240.

In the breech bolt 3, whose path of movement lies above the breechcasing 2, a groove 27 is cut, the rear boundary of which is formed as anengaging portion by the incline 3a, which leads into a control face 3bparallel to the path of movement of a projection of the breech bolt.

From this construction results the following manner of operation:referring again to FIG. 1, the firing mechanisrn is here illustrated inits initial position. The looking slide 8 abuts with its rear end face8e the wall 2:: of the casing 2. Under the bias of a return spring 29the breech bolt bears with its incline 3a on the engaging face 18a ofthe lock catch 18 and thereby applies a moment to the sear 16, whichtends to release the same, but cannot turn it owing to the forwardportion of the locking slide 8 lying under the face 16b thereof. Whenthe breech bolt 3 is to be released, this is effected by actuating thetrigger mechanism, i.e. the arm 10a of the trigger 16 is raised, byraising the face 12 and by its other arm 16b the locking slide 8 isforced forward (to the left) while simultaneously loading the spring 15.During this forward movement the detent member 24 is raised against thebias of the spring 26 by the cam face 8c of the locking slide 8 abuttingits face 240, whereby the detent member 24 is slightly turned clockwiserelative to the tumbler 22 which remains unmoved. Thereby the cam faces8c, 8:! of the locking slide 8 can move forward under and past thedetent member 24. Moreover the forward portion of the locking slide 8acting as a bolster slides away under the face 16b of the sear 16, sothat the bolstering thereof is abolished. At the same time the forwardface 8b of the locking slide 8 abuts the projection face 21!) of thesear 16, whereby an additional rotational impulse is applied to thelatter, which reinforces now its turning into the release positionillustrated in FIG. 2 (now made possible by the bolstering thereof beingabolished), in which position then the sear 16 is arrested by thelocking slide acting on its projection 21. The breech bolt 3 released bythe sear 16, lock catch 18 thereof respectively can now move forward,i.e. to the left of FIG. 2. This condition is preserved, as long as thetrigger mechanism is being pulled, i.e. in the case of a series ofshots.

Referring now again to FIG. 3: when the trigger mechanism is releasedi.e. the face is lowered in direction of arrow, for the purpose ofinterrupting the firing, nothing happens at first until the moment atwhich the projection of the breech bolt 3 the control face 3b thereofrespectively no longer overlaps the tumbler 22. Thereby the overlappingis abolished, and by the turning of the trigger 10, which is now madepossible, and owing to the bias of the spring 15 the locking slide 8 isdriven towards the right. By the cam face 8d of the locking slide 8abutting the face 24b of the detent member 24 a pressure is applied tosaid face 24b which is transmitted to the tumbler 22. The latter anddetent member 24 can now leave their rest portion and give way. It turnsclockwise until it abuts the spring sleeve 13, i.e. until its face 22aprotrudes into the path of the breech bolt 3. During this turning of thetumbler 22, the cam faces 8c, 8d move away under the detent member 24.At the same time the locking slide 8 releases the projection 21 of thesear 16, so that the same turns counterclockwise under the bias of thespring 28 upon the bearing surface 16c about the pivot 17 until the face21a abuts the bottom of the support 7, and the engaging face 13a of thelock catch 18 protrudes into the path of the breech bolt 3. After thepassing of the cam faces 80, 8d underneath the detent member 24, thelatter returns again into the rest position together with the tumbler22, under the bias of the spring 26 When the breech bolt 3 is in theposition shown in chain-dotted lines in F16, 2, i.e. with its controlface 3b above the curved face 22a of the tumbler 22, a return movementof the sear 16 into the fully holding position is impossible; for inspite of the thrust applied by the locking slide 8 to the detent member24, the tumbler 22 cannot be moved, being held down by the projection ofthe breech bolt 3. The detent member 24 then remains in its restposition, and the locking slide 8 can release the sear 16 for beingturned into the holding position then only, when the advancing breechbolt 3 has slid with its control face 3b past the face 22a of thetumbler 22, and the latter turns upward together with the detent member24 under the thrust of a locking slide 8.

The tumbler 22 accordingly acts as the control member for the lockingslide 8. While being overlapped by the breech bolt 3 it prevents thelocking slide 8 from releasing the sear 16 for turning into the holdingposition already at a moment, when, as in the position of the breechbolt indicated in FIG. 2 in chain-dotted lines, the time is no longersufficient for turning the engaging face 18a of the lock catch 18 ingood time sutficently high into the path of the incline 3a for engagingthe same for full area contact, before the passing of the breech bolt 3advancing again after its rear reversal.

However, when after releasing the trigger mechanism, the lock catch 18has been returned into the path of the recoiling breech bolt 3 (movingto the right in the figure), the nose is resiliently depressed by saidbolt running up its face 18b and is turned clockwise about the pivot 19and thereby swung out of the path of the breech bolt 3 so that thelatter can pass unhampered. After the running-over of the lock catch 18is terminated, the latter is returned by the spring 20 to the holdingposition in order to catch the advance movement of the breech bolt 3after the rear reversal thereof, in the initial position illustrated inFIG. 1, whereby the firing is terminated.

While I have described herein, and illustrated in the accompanyingdrawing what may be considered a typical and particularly usefulembodiment of my said invention I wish it to be understood that I do notlimit myself to the particular details and dimensions described andillustrated; for obvious modifications will occur to a person skilled inthe art.

What I claim as my invention, and desire to secure by Letters Patent,is:

1. A firing mechanism for automatic firearms comprising in combination asupport, a pivot on said support, a breech bolt having a control facereciprocating in operation on said support on a linear path of motion,an inclined surface on said breech bolt adjacent said control faceinclined towards said path of motion at an inclination of less than areturn spring acting on said breech bolt for the forward motion of saidbreech bolt, holding means for locking said breech bolt in an initialposition, said holding means comprising a sear pivotable on said pivothaving a stop face, an auxiliary pivot spaced from said pivot on saidsear, a lock catch for said breech bolt pivotable on said auxiliarypivot having an engaging face cooperating with said inclined surface andan engaging face cooperating with said stop face, an auxiliary springfor the adjustment of said lock catch cooperating with said sear andsaid lock catch, spring means acting on said sear for loading said searin the direction to breech bolt holding position, means for rotatingsaid sear from said holding position to release position, said lastnamed means comprising a locking slide operable by a trigger mechanismmovably guided on said support along a line of displacement, said searhaving a projection extending into the range of said line ofdisplacement whereby said sear may be moved by said slide against theeffect of said spring means.

2. A firing mechanism as claimed, in claim 1, wherein a breach casing isprovided and said support is mounted longitudinally slidable in saidbreech casing with resilient and damping means abutting said breechcasing.

3. A firing mechanism for automatic firearms comprising in combination asupport, a breech bolt reciprocating longitudinally relative to saidsupport on a straight path of motion, with a rear reversal and a lastportion of said path of motion in front of said rear reversal and afirst portion behind said reversal, with an initial position on saidpath, an incline on said breech bolt sloped towards said path, a controlface on said breech bolt adjoining said incline towards the rear,holding means pivotally mounted on said support having an engaging faceextending towards said incline, a projection on said holding means, saidholding means having a release position in which said engaging face iskept outside the range of said incline and a holding position in whichsaid engaging face extends into said path, said holding means having abearing surface and a supporting surface, a spring supported on one sideon said support and on the other side on said bearing surface, saidspring urging a rotation of said holding means to holding position, alocking slide having an operating surface and two cam faces movable to alocking position and an opening position so that upon movement from saidlocking position into said opening position said projection is moved bysaid slide thereby rotating said holding means into release position,with said operating surface in the locking position of said lockingslide, supporting said holding means at said supporting surface withsaid cam faces being behind said operating surface, detent meanscomprising a detent member, a tumbler with a convex face, said convexface cooperating with said control face of said breech bolt, said lastportion of said breech bolt path being in front of said rear reversaland said first portion behind said reversal, said tumbler cooperatingwith said detent member for locking the movement of said cam faces intosaid locking position of said locking slide and for releasing said camfaces for movement into said opening position of said locking slide.

4. A firing mechanism as claimed in claim 3, wherein the engagingportion of said breech bolt has at least a length sufiicient to keepsaid detent means depressed in the rest position until during theadvance stroke of said breech bolt said incline is in juxtaposition withsaid engaging face of said holding means.

References Cited in the file of this patent UNITED STATES PATENTS2,524,258 Hepperle Oct. 3, 1950 2,765,709 Hepperle et al. Oct. 9, 19562,905,058 Maillard Sept. 22, 1959 FOREIGN PATENTS 716,924 Germany Feb.2, 1942 925,158 Germany Mar. 14, 1955

1. A FIRING MECHANISM FOR AUTOMATIC FIREARMS COMPRISING IN COMBINATION ASUPPORT, A PIVOT ON SAID SUPPORT, A BREECH BOLT HAVING A CONTROL FACERECIPROCATING IN OPERATION ON SAID SUPPORT ON A LINEAR PATH OF MOTION,AN INCLINED SURFACE ON SAID BREECH BOLT ADJACENT SAID CONTROL FACEINCLINED TOWARDS SAID PATH OF MOTION AT AN INCLINATION OF LESS THAN 90*,A RETURN SPRING ACTING ON SAID BREECH BOLT FOR THE FORWARD MOTION OFSAID BREECH BOLT, HOLDING MEANS FOR LOCKING SAID BREECH BOLT IN ANANIMAL INITIAL POSITION, SAID HOLDING MEANS COMPRISING A SEAR PIVOTABLEON SAID PIVOT HAVING A STOP FACE, AN AUXILIARY PIVOT SPACED FROM SAIDPIVOT ON SAID REAR, A LOCK CATCH FOR SAID BREECH BOLT PIVOTABLE ON SAIDAUXILIARY PIVOT HAVING AN ENGAGING FACE COOPERATING WITH SAID INCLINEDSURFACE AND AN ENGAGING FACE COOPERATING WITH SAID STOP FACE, ANAUXILIARY SPRING FOR THE ADJUSTMENT OF SAID LOCK CATCH COOPERATING WITHSAID SEAR AND SAID LOCK CATCH, SPRING MEANS ACTING ON SAID SEAR FORLOADING SAID SEAR IN THE DIRECTION TO BREECH BOLT HOLDING POSITION,MEANS FOR ROTATING SAID SEAR FROM SAID HOLDING POSITION TO RELEASEPOSITION, LAST NAMED MEACH COMPRISING A LOCKING SLIDE OPERABLE BY ATRIGGER MECHANISM MOVABLY GUIDED ON SAID SUPPORT ALONG A LINE OFDISPLACEMENT, SAID SEAR HAVING A PROJECTION EXTENDING INTO THE RANGE OFSAID LINE OF DISPLACEMENT WHEREBY SAID SEAR MAY BE MOVED BY SAID SLIDEAGAINST THE EFFECT OF SAID SPRING MEANS.